JP4872974B2 - Wireless communication device - Google Patents

Description

  The present invention relates to a wireless communication apparatus used in a wireless communication system in which a plurality of communication terminals perform wireless communication via a common wireless communication channel.

  In wireless communication, in order to avoid mutual interference, a dedicated frequency band is generally assigned to each wireless communication system. However, radio waves from adjacent communication channels and radio waves from other systems may be generated in this allocated communication band, resulting in interference. In order to effectively use a limited frequency, the same frequency band may be used in a plurality of communication systems. In this case, interference from other systems is received in the same frequency band.

In order to avoid and reduce such interference, conventionally, various proposals such as the following (1) to (4) have been made.
(1) In the spread spectrum communication apparatus, the reception-side radio measures the communication quality of the desired wave and notifies the measurement result to the transmission-side radio, and the transmission-side radio sets the notified communication quality. Based on this, the transmission power is controlled to ensure the communication quality of the desired wave (see, for example, Patent Document 1).
(2) In a radio communication system composed of a base station and a terminal station, a variable attenuator for controlling the signal power input to the receiving device to a reference level on the base station side, and a terminal side based on the received power By providing a transmission power control device for setting the transmission power of the terminal and instructing the terminal side, the transmission power on the terminal side is increased when an interference wave exists, and the S / N of the received signal input to the reception device is increased. (For example, see Patent Document 2).
(3) The mobile terminal predicts the relative distance between the own terminal and the communication partner, and controls transmission power based on the predicted relative distance, thereby avoiding unnecessary interference (see, for example, Patent Document 3). .
(4) In the wireless communication system, the reception side measures the received signal strength and noise level and transmits the response packet in the response packet to the transmission side, and the transmission side receives the received signal strength and noise level included in the response packet. By adjusting the communication speed according to the above, the communication speed is adjusted in real time for each packet while suppressing an increase in traffic (see, for example, Patent Document 4).
JP 2000-165290 A JP 2002-198834 A JP 2007-6395 A JP 2005-286405 A

  All of the proposed wireless communication systems transmit some control information from the reception side so that optimum reception can be performed without being affected by interference waves on the reception side, and transmission is performed according to the control information on the transmission side. It is designed to control power and communication speed.

  For this reason, if the proposed technique is applied to a wireless communication system in which each communication terminal performs one-to-one communication with another communication terminal, interference waves from other systems and adjacent channels are transmitted between the communication terminals. The influence can be reduced and good wireless communication can be performed.

  However, since the proposed technique is based on the premise that the communication terminal performs one-to-one communication, each communication terminal wirelessly transmits to other communication terminals via a wireless channel common to each terminal. It cannot be applied to a many-to-many wireless communication system (for example, a broadcast-type wireless communication system), and a wireless communication apparatus used in such a wireless communication system depends on the states of a plurality of other communication terminals. Communication parameters could not be controlled.

  The present invention has been made in view of these problems. In a many-to-many wireless communication system in which a plurality of communication terminals perform wireless communication via a common wireless communication channel, each communication terminal is connected to another system or an adjacent channel. It is an object of the present invention to enable good wireless communication without being affected by interference waves from.

  The wireless communication apparatus according to claim 1, wherein the measurement means measures a noise level in a wireless communication channel used for wireless communication with a plurality of other communication terminals. Then, the transmission means transmits the measured noise level to a plurality of other communication terminals as a part of the transmission data.

  Further, when receiving means receives a transmission radio wave from another communication terminal, the receiving means restores the received data from the received signal, and further, the noise level included in the restored received data (that is, the communication that has transmitted the received data). (Noise level around the terminal) is extracted.

  Then, the control means converts the noise level around the wireless communication device (hereinafter also referred to as own terminal) measured by the measurement means and the noise levels around other communication terminals extracted by the reception means. Based on this, communication parameters for performing wireless communication with a plurality of other communication terminals are controlled.

  Therefore, according to the wireless communication device of the first aspect, noise is generated between the plurality of communication terminals based on the noise level around the own terminal and the noise levels around the plurality of communication terminals serving as communication partners. Communication parameters necessary for performing wireless communication without being affected by (that is, interference waves) can be set. In a wireless communication system that performs many-to-many communication such as a broadcast-type wireless communication system, each communication terminal The communication quality between them can be improved.

  Here, as described in claim 2, the noise level around the other communication terminal that is the communication partner is stored in the storage means for each communication terminal that has transmitted the noise level. May be added, updated, or deleted according to the noise level extraction state by the receiving means.

  In other words, in this way, when the reception means restores the reception data from the communication terminal whose noise level is not stored in the storage means, the noise level contained in the reception data is changed to a new communication terminal. When the received data from the communication terminal whose noise level is stored in the storage means is received by the receiving means, it is stored in the storage means based on the noise level included in the received data. When the reception data from the communication terminal whose noise level is stored in the storage means is not received for a long time at the receiving means, the communication terminal has stopped transmitting data or moved. It is possible to determine and delete the noise level of the communication terminal from the storage means, and control communication parameters. A plurality of noise levels which are can be always up to date.

  Further, in this way, even in a wireless communication system for mobile communication in which a communication terminal moves, the present invention can be applied to optimally control communication parameters used by each communication terminal for wireless communication. Become.

  Next, when the control means controls the communication parameter, for example, as described in claim 3, the noise level measured by the measurement means and a plurality of noise levels extracted by the reception means are selected. The highest noise level may be selected, and the communication parameter may be controlled based on the selected noise level. Alternatively, the noise level measured by the measuring unit and the receiving unit as described in claim 4. The average value or median value of the noise levels may be calculated based on the plurality of noise levels extracted in step 1, and the communication parameter may be controlled based on the calculated average value or median value.

  When the communication parameter is controlled based on the maximum noise level as described in claim 3, communication suitable for the communication terminal having the worst communication environment including its own terminal can be performed. .

  In addition, as described in claim 4, when the communication parameter is controlled based on the average value or the median value of the noise level, the communication parameter is controlled based on the maximum noise level. Thus, it is possible to prevent the control parameter from being controlled more than necessary, and to perform wireless communication suitable for many of the plurality of communication terminals.

  Next, the communication parameters controlled by the control unit based on a plurality of noise levels are, for example, transmission power of transmission data from the transmission unit, modulation scheme of transmission data, and transmission data as described in claim 5. One of these coding rates, or a combination thereof, or, as described in claim 6, one or both of the carrier sense level and the receiving sensitivity in the receiving means may be used.

  If the control means controls the communication parameters (transmission power, modulation scheme, coding rate, etc.) used by the transmission means to transmit data as described in claim 5, the own terminal Communication quality at the time of transmitting data to other communication terminals can be improved. As described in claim 6, the communication means (carrier sense level, reception sensitivity, etc.) used by the control means for receiving data by the control means. ), It is possible to improve communication quality when the own terminal receives transmission data from other communication terminals.

  For this reason, in order to further improve the communication quality of the entire wireless communication system, the control means includes communication parameters (transmission power, modulation scheme, coding rate, etc.) used by the transmission means to transmit data, and a reception means. It may be configured to control both communication parameters (carrier sense level, reception sensitivity, etc.) used for receiving data.

  In addition, in this way, the control means uses communication parameters (transmission power, modulation scheme, coding rate, etc.) used by the transmission means to transmit data, and communication parameters (carrier sense) used by the reception means to receive data. In a case where both the level, reception sensitivity, etc.) are controlled, it may be as described in claim 7.

  That is, in the radio communication apparatus according to claim 7, the control means, based on a plurality of noise levels extracted by the reception means, transmission power of transmission data from the transmission means, modulation scheme of transmission data, and transmission At least one of the data coding rates is controlled, and at least one of the carrier sense level and reception sensitivity in the receiving means is controlled based on the noise level measured by the measuring means.

  Therefore, according to the wireless communication device of the seventh aspect, the communication parameter related to transmission and the communication parameter related to reception can be individually controlled using the noise levels corresponding to the communication parameter. Appropriate communication control can be performed even when there is a difference in noise level between the communication terminal and other communication terminals.

  On the other hand, in the radio communication device according to claim 8, as in the radio communication device according to claims 1 to 7, the measurement unit measures the noise level around the terminal itself, but the transmission unit measures the noise level. In addition to the generated noise level, position data representing the position of the own terminal is transmitted to a plurality of other communication terminals as a part of transmission data.

  In addition, when receiving means receives a transmission radio wave from another communication terminal, the receiving means restores the received data from the received signal, and further, from the restored received data, the noise level around the communication terminal that transmitted the received data And extract position data.

  Then, based on the position data extracted by the receiving means, the distance calculating means calculates the distance between the communication terminal corresponding to the position data (that is, the communication terminal that has transmitted the received data) and the own terminal, and the control means Controls communication parameters for wireless communication with other communication terminals based on a plurality of noise levels extracted by the receiving means and a plurality of distances calculated by the distance calculating means. To do.

  For this reason, according to the wireless communication device of the eighth aspect, the communication parameter is obtained by using the noise level around the plurality of other communication terminals serving as communication partners and the distance between each communication terminal and the own terminal. Can be more optimally controlled, and communication quality in a wireless communication system that performs many-to-many communication can be further improved.

  Here, as in the present invention, when the communication parameter is further controlled using the noise level around the plurality of communication terminals and the distance between each of the communication terminals and the own terminal, As described above, the control means may calculate the control coefficient based on the noise level and the distance for each communication terminal that has transmitted the reception data, and control the communication parameter based on the calculated plurality of control coefficients. . In this way, the communication parameter can be easily controlled using the control coefficient calculated from the noise level and the distance.

  Further, when the control parameter is controlled using the control coefficient calculated from the noise level and the distance as described above, the calculated control coefficient is set for each corresponding communication terminal as described in claim 10. The control coefficient stored in the storage means may be added / updated / deleted according to the noise level and the position data extracted by the receiving means.

  In other words, in this way, as in the above-described claim 2, the control coefficient can be updated to the latest corresponding to the communication terminal that actually exists around the terminal and performs wireless communication. Even if the wireless communication system to which the invention is applied is a wireless communication system for mobile communication, it is possible to optimally control communication parameters used by each communication terminal for wireless communication.

  Next, when the control means controls the communication parameter, for example, as described in claim 11, the largest control among a plurality of control coefficients calculated for each communication terminal from the noise level and the distance. The coefficient may be selected and the communication parameter may be controlled based on the selected control coefficient, or an average value of a plurality of control coefficients calculated from the noise level and the distance or The median value may be calculated, and the communication parameter may be controlled based on the calculated average value or median value.

  Then, as described in claim 11, when the communication parameter is controlled based on the maximum control coefficient, it is suitable for the communication terminal having the worst communication environment as in the case of claim 3. When communication is enabled and the communication parameter is controlled based on the average value or the median value of the control coefficients as described in claim 12, the control is performed as in the case of claim 4. It is possible to prevent the parameters from being controlled more than necessary, and to perform wireless communication suitable for many other communication terminals.

  Further, the control means, as described in claim 13, based on the control coefficient, one of transmission power of transmission data from the transmission means, modulation method of transmission data, and coding rate of transmission data, These combinations may be configured to be controlled, or, as described in claim 14, configured to control one or both of the carrier sense level and the reception sensitivity in the receiving unit based on the control coefficient. Also good.

  If the control means controls communication parameters (transmission power, modulation scheme, coding rate, etc.) used by the transmission means to transmit data as described in claim 13, Communication quality at the time of transmitting data to other communication terminals can be improved. As described in claim 14, communication parameters (carrier sense level, reception sensitivity, etc.) used by the control means for receiving data by the control means. ), It is possible to improve communication quality when the own terminal receives transmission data from other communication terminals.

  For this reason, in order to further improve the communication quality of the entire wireless communication system, the control means includes communication parameters (transmission power, modulation scheme, coding rate, etc.) used by the transmission means to transmit data, and a reception means. It may be configured to control both communication parameters (carrier sense level, reception sensitivity, etc.) used for receiving data.

  In addition, in this way, the control means uses communication parameters (transmission power, modulation scheme, coding rate, etc.) used by the transmission means to transmit data, and communication parameters (carrier sense) used by the reception means to receive data. In a case where both the level, the reception sensitivity, etc.) are controlled, it may be as described in claim 15.

  That is, in the wireless communication device according to claim 15, the control means transmits transmission data from the transmission means based on a control coefficient calculated from a noise level around another communication terminal and a distance between the other communication terminal and the own terminal. And at least one of the carrier sense level and the reception sensitivity in the receiving means based on the noise level measured by the measuring means. Control one.

  Therefore, according to the wireless communication device of claim 15, the communication parameter related to transmission and the communication parameter related to reception can be individually controlled according to the control coefficient or the noise level of the own terminal, Appropriate communication control can be performed even when there is a difference in noise level between the own terminal and another communication terminal.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing the configuration of the wireless communication apparatus according to the first embodiment.

  The wireless communication device 2 according to the present embodiment is, for example, for carrying out wireless communication with a vehicle around the host vehicle or other communication terminals arranged near the traveling path of the vehicle. The transmitter 10 and the receiver 30 are connected to the antenna 4 via the transmission / reception switching unit 6.

  The transmission unit 10 includes a modulation unit 12 that modulates transmission data into a predetermined transmission signal, a frequency converter 14 that converts the transmission signal from the modulation unit 12 to a frequency band of a preset wireless communication channel, and a frequency A high frequency amplifier 16 that amplifies the transmission signal whose frequency has been changed by the converter 14 is provided, and the transmission signal amplified by the high frequency amplifier 16 is output to the antenna 4 via the transmission / reception switching unit 6. A transmission signal is wirelessly transmitted from the antenna 4.

  The receiving unit 30 also receives a signal received by the antenna 4 and amplifies the received signal input via the transmission / reception switching unit 6, and the received signal amplified by the high frequency amplifier 32 is converted into a baseband received signal. A frequency converter 34 that performs frequency conversion, a demodulator 36 that restores data (received data) transmitted from other communication terminals from the received signal that has been frequency converted by the frequency converter 34, and a wireless communication from the frequency converter 34. There is provided a noise level measuring unit 40 that takes in a received signal corresponding to a communication channel and measures its noise level.

  The noise level measuring unit 40 is for measuring the total noise level such as interference power and thermal noise received from other systems and adjacent channels in the wireless communication channel used by the wireless communication apparatus 2 for wireless communication. is there.

  Various methods are conventionally known as methods for measuring the noise level. In this embodiment, when the demodulator 36 is not performing demodulation processing, the signal level of the received signal is measured and the measured value is measured. Is the noise level.

  For this reason, the noise level measurement unit 40 receives a signal from the demodulation unit 36 indicating whether demodulation processing is being performed (for example, whether a preamble included in a transmission signal from another communication terminal has been detected). Have been entered.

Next, the measurement result (noise level data) of the noise level by the noise level measurement unit 40 is output to the modulation unit 12 of the transmission unit 10.
Then, the modulation unit 12 inserts the noise level data into the transmission data, and as illustrated in FIG. 2, from the MAC header, the network header, the noise level data, the transmission data, the FCS (Frame Check Sequence), etc. A transmission signal is generated, and a transmission signal is generated by modulating a carrier wave with the transmission packet.

  For this reason, in the wireless communication system configured using the wireless communication device 2 of the present embodiment, the noise level data measured on the other communication terminal side is also included in the transmission packet from the other communication terminal. .

  Then, the demodulator 36 extracts noise level data from the received data restored from the received signal, and outputs the noise level data and the identification information of the communication terminal that has transmitted this data to the transmitter 10. To do.

  On the other hand, the transmitter 10 is used to determine the presence / absence of a received signal from the power of the transmission signal output from the high frequency amplifier 16 (that is, transmission power) and the signal level of the wireless communication channel on the demodulator 36 side. A control unit 20 that controls a carrier sense level (hereinafter referred to as a CS level) is provided.

  The noise level data and communication terminal identification information output from the demodulator 36 to the transmitter 10 are input to the controller 20. The noise level measured by the noise level measuring unit 40 is also input to the control unit 20 as noise level data of the terminal itself.

  The control unit 20 is composed of a microcomputer or the like, and writes the noise level data input from the demodulation unit 36 and the noise level measurement unit 40 to the storage unit (memory) 22 together with the identification information of the communication terminal and its update time. As a result, as shown in FIGS. 3B and 3C, a noise table is generated that represents the noise levels around all communication terminals capable of wireless communication and the wireless communication apparatus 2 (own terminal).

  That is, in the noise table shown in FIGS. 3B and 3C, a plurality of communication terminals a to i are arranged as shown in FIG. 3A, and each communication terminal a to i is a dotted line in the figure. The noise table generated by the communication terminals c and g when wireless communication is possible along the route indicated by.

  As is apparent from this figure, for example, in the communication terminal c, the noise level data acquired from the communication terminals a, b, d, e capable of wireless communication, the noise level data of the own terminal c, A noise table including identification information a, b, d, e, c and update times ta, tb, td, te, tc of each noise level data is generated and stored in the storage unit 22.

FIG. 4 is a flowchart showing processing executed by the control unit 20 to generate / update the noise table.
As shown in FIG. 4, in the control unit 20, as a process for generating / updating a noise table, a data deletion process for deleting unnecessary noise level data and data for adding or updating noise level data Addition / update processing is executed.

  The data deletion process checks the update time of each noise level data in the noise table (S120) every time a predetermined time set in advance for deletion determination elapses (S110-YES). It is determined whether or not there is noise level data that has not been updated since the previous check, and if there is noise level data that has not been updated since the previous check, it is deleted (S130).

  Further, in the data addition / update process, when noise level data is input from the receiving unit 30 side (S140-YES), the noise level data of the same terminal as the input noise level data is stored in the noise table. If there is noise level data of the same terminal (S160: YES), the noise level data of the corresponding terminal is updated using the noise level data input this time (S170). If there is no noise level data of the terminal (S160: NO), the noise level data input this time is added to the noise table (S180).

  As a result, the noise table in the storage unit 22 responds to changes even if the communication terminal capable of wireless communication changes due to movement of the own terminal or another communication terminal, or the noise level around the communication terminal changes. Thus, the control unit 20 can always grasp the status of surrounding communication terminals.

  When updating or adding the noise level data in S170 and S180 of FIG. 4, it is not always necessary to write the latest noise level data. For example, the average value of the noise levels input a plurality of times in the past is written. Anyway. By doing so, the variation in the noise level data is reduced, and stable control is possible.

  The control unit 20 controls the transmission power (specifically, the amplification factor of the high-frequency amplifier 16) and the CS level in the demodulation unit 36 using the noise table generated and updated as described above. The maximum noise level data selected from the noise level data in the noise table is used.

  Then, the control unit 20 performs control using the selected maximum noise level data, the transmission power setting map shown in FIG. 5 (a), and the CS level setting map shown in FIG. 5 (b). Set the transmit power and CS level to be used.

  Here, the transmission power setting map shown in FIG. 5 (a) controls the transmission power between the basic transmission power and the maximum transmission power because the upper limit of the transmission power is determined by the characteristics of the high frequency amplifier 16. The control unit 20 sets the maximum and minimum noise levels corresponding to the basic transmission power and the maximum transmission power as threshold values 1 and 2, and the maximum noise level data selected from the noise table. Is set within the range of threshold value 1 to threshold value 2, transmission power is set according to the noise level data. When the maximum noise level data is equal to or lower than threshold value 1 or threshold value 2, the transmission power is set to the basic transmission power. Alternatively, the maximum transmission power is set.

  In addition, the CS level setting map shown in FIG. 5B is set to control the CS level between the basic CS level and the maximum CS level, similarly to the transmission power setting map. The control unit 20 sets the upper and lower limit values of the noise level corresponding to the basic CS level and the maximum CS level as the threshold value 1 and the threshold value 2, and the maximum noise level data selected from the noise table ranges from the threshold value 1 to the threshold value 2. The CS level is set according to the noise level data, and when the maximum noise level data is less than or equal to threshold 1 or greater than or equal to threshold 2, the CS level is set to the basic CS level or the maximum CS level. .

  In the maps shown in FIGS. 5A and 5B, when the noise level data is within the control range of the threshold value 1 to the threshold value 2, the transmission power or the CS level is linear with respect to the change of the noise level. Although it is set so as to change, this characteristic may be such that the transmission power and the CS level change stepwise or in a curve with respect to the change of the noise level.

When the controllable range of transmission power and CS level is sufficiently wide, it is not necessary to limit the upper and lower limits of the noise level data used for control by providing the threshold values 1 and 2 as described above.
The control of the transmission power and the CS level in the control unit 20 may be performed periodically at regular time intervals, or may be performed when transmission data is input to the transmission unit 10.

  Next, in FIG. 6, a plurality of communication terminals a to i configured in the wireless communication device 2 of the present embodiment are arranged as illustrated in FIG. It is explanatory drawing showing the transmission power and CS level controlled by each communication terminal ai when a noise level is a noise level shown to Fig.3 (a).

  In FIG. 6, the threshold 1, threshold 2, basic transmission power, and maximum transmission power, which are control parameters for transmission power, are set to −90 dBm, −80 dBm, 10 dBm, and 20 dBm, respectively, and are control parameters for the CS level. It is assumed that the threshold value 1, the threshold value 2, the basic CS level, and the maximum CS level are set to −90 dBm, −80 dBm, −80 dBm, and −70 dBm, respectively.

  As shown in FIG. 6, among the communication terminals a to i, in the communication terminals d, e, f, g, h, and i, the maximum noise level data among the own terminal and the surrounding terminals is −80 dBm. Therefore, transmission power and CS level are controlled based on this value.

  Since this noise level data “−80 dBm” corresponds to the threshold value 2 of the control parameter of the transmission power and CS level, the transmission power is the maximum transmission power at the communication terminals d, e, f, g, h, i. The CS level is controlled to “20 dBm”, and the CS level is controlled to the maximum CS level “−70 dBm”.

  On the other hand, in the communication terminals a, b, and c, the maximum noise level data among the own terminal and the surrounding terminals is −86 dBm. Based on this value, the transmission power is controlled to 14 dBm, and the CS level is It will be controlled to -76 dBm.

  As described above, in the wireless communication device 2 of the present embodiment, the noise level data of the own terminal and the noise level data acquired from the surrounding communication terminals are stored as a noise table, and the maximum noise level data in the noise table is stored. To control the transmission power and the CS level.

  Therefore, according to the wireless communication device 2 of the present embodiment, the transmission power at the time of data transmission and the received signal detection CS level are affected by noise (that is, interference waves) with a plurality of surrounding communication terminals. It is possible to set an optimal value for wireless communication without receiving, and to improve communication quality between communication terminals in a wireless communication system that performs many-to-many communication. Become.

In the present embodiment, the modulation unit 12, the frequency converter 14 and the high frequency amplifier 16 constituting the transmission unit 10 correspond to the transmission unit of the present invention, and the control unit 20 corresponds to the control unit of the present invention. The storage unit 22 corresponds to the storage unit of the present invention. Further, the high-frequency amplifier 32, the frequency converter 34, and the demodulation unit 36 constituting the receiving unit 30 correspond to the receiving unit of the present invention, and the noise level measuring unit 40 corresponds to the measuring unit of the present invention.
(Modification 1)
Here, in the present embodiment, the noise level data having the maximum noise level is selected from the noise table and the transmission power and the CS level are calculated, but this is used to calculate the transmission power and the CS level. It is not always necessary to use the maximum noise level data. For example, an average value or a median value of all noise level data stored in the noise table may be used. In this way, it is possible to control the transmission power and the CS level to values suitable for more communication terminals as compared with the case where the maximum noise level data is used.
(Modification 2)
In the present embodiment, the transmission parameter and the CS level are controlled as communication parameters. However, other modulation parameters such as a modulation method and a coding rate of the transmission data in the modulation unit 12 or reception sensitivity of the received signal are used. Communication parameters may be controlled.

  When the modulation scheme and coding rate are controlled in addition to the transmission power and the CS level, as shown in FIG. 7A, the control unit 20 uses the transmission rate setting setting shown in FIG. 7B. Is used to calculate the transmission rate from the maximum noise level data (or the average value or median value of the noise level data) and control the modulation scheme or coding rate in the modulation unit 12 according to the transmission rate. You just have to do it.

  That is, the probability that the transmission data can be restored on the receiving side is increased by controlling the modulation scheme or coding rate so that the transmission rate decreases as the noise level increases. In this way, more reliable communication is possible.

Such modulation scheme and coding rate control may be performed simultaneously with transmission power control or separately. Each of these controls may be performed using different noise level data (for example, maximum value and average value).
(Modification 3)
Next, in the present embodiment, the transmission power and the CS level have been described as being controlled based on the maximum noise level data stored in the noise table. Control may be performed using the maximum value of the noise level data of the terminal, and the CS level may be controlled using the noise level data of the terminal itself measured by the noise level measurement unit 40.

  In this case, in the plurality of communication terminals a to i illustrated in FIG. 3A, the transmission power and the CS level are controlled as illustrated in FIG. In the communication terminal c having higher noise level data than a, b, d, and e, the transmission power is calculated using the maximum value (−88 dBm) of the noise level data in the surrounding communication terminals a, b, d, and e. Since the transmission power is controlled, the transmission power becomes a value (12 dBm) lower than the transmission power (14 dBm) of the above embodiment, and the transmission radio wave from the antenna 4 can be prevented from reaching more than necessary.

  Further, in the present modification, the CS level is set using the noise level data of the terminal itself. For example, in the above embodiment, the communication terminal g in which the ambient noise level is high and the CS level is controlled to “−70 dBm”. In this case, the CS level is controlled to be “−80 dBm” based on the noise level data (−90 dBm) of the own terminal, and the possibility that a transmission signal from another communication terminal is missed is reduced. it can.

That is, as in Modification 3, the communication parameters for transmission such as transmission power and the communication parameters for reception such as CS level are based on the noise level of surrounding communication terminals and the noise level of the own terminal. If individually controlled, communication control can be performed satisfactorily when there is a difference in noise level between the own terminal and another communication terminal.
(Second Embodiment)
Next, a second embodiment of the present invention will be described.

FIG. 9 is a block diagram illustrating the configuration of the wireless communication device 2 of the present embodiment.
The wireless communication apparatus 2 of the present embodiment has substantially the same configuration as that of the first embodiment shown in FIGS. 1 and 7, and differs from that of the first embodiment in that navigation mounted on a vehicle. This is that position data representing the current position is input to the modulation unit 12 and the control unit 20 from a device or the like.

Therefore, in the following description, the modulation unit 12 and the control unit 20 to which position data is input as described above will be mainly described, and description of the same parts as those in the first embodiment will be omitted.
The position data includes absolute coordinates obtained from the GPS receiver, a relative position with a fixed point (for example, a mobile phone base station, a roadside device in an in-vehicle communication environment), and a position on the road recognized by the navigation device. , Etc.

  First, the modulation unit 12 adds the position data to the transmission packet shown in FIG. 2 by inserting the noise level data measured by the noise level measurement unit 40 and the position data into the transmission data. 10 is generated, and a transmission signal is generated by modulating a carrier wave with the transmission packet.

  For this reason, in the wireless communication system configured using the wireless communication device 2 of the present embodiment, the noise level data measured on the other communication terminal side and the position of the communication terminal are also included in the transmission packet from the other communication terminal. Is included.

If position data is already included in the transmission data, the modulation unit 12 does not need to insert position data into the transmission data.
Next, similarly to the first embodiment, the control unit 20 uses a noise level data of another communication terminal input from the demodulation unit 36 to control a communication parameter (transmission power, CS level, etc.). However, in the present embodiment, since the position data is included in the received data from other communication terminals, the noise level data and the position data are input from the demodulator 36 to the controller 20, A control table is created using two types of data.

  That is, when the position data is input from the demodulation unit 36, the control unit 20 calculates a distance x with another communication terminal that has transmitted the position data based on the position data and the position data of the host vehicle. Based on this distance x and the noise level data (that is, the noise level (true number) n on the other communication terminal side) input together with the position data from the demodulator 36, the control coefficient f (x , N).

なお、上記演算式において、「ｘmax 」は、他の通信端末との所望最大通信距離を表し、「ｎmax 」は、考慮すべき最大ノイズレベル（真数）を表し、「ｊ」、「ｋ」は、重み付けのための定数を表す。

In the above equation, “xmax” represents a desired maximum communication distance with another communication terminal, “nmax” represents a maximum noise level (integer) to be considered, and “j”, “k”. Represents a constant for weighting.

  According to the above arithmetic expression, the control coefficient f (x, n) increases as the distance from the other communication terminal increases, and the control coefficient f ( x, n) increases.

  Next, the control unit 20 stores the control coefficient f (x, n) calculated as described above together with the identification information of the communication terminal that has transmitted the position data and the noise level data and the update time thereof, and the storage unit (memory) 22. As shown in FIGS. 11B and 11C, a data table of the control coefficient f (x, n) is generated.

  In addition, as shown in FIG. 11A, the data table shown in FIGS. 11B and 11C includes five communication terminals a to e that can communicate with each other in a straight line at predetermined intervals. The data table generated by the communication terminals a and e at both ends is shown.

And this data table is produced | generated and updated according to the reception state of the data from the other communication terminal in the demodulation part 36 similarly to the noise table of 1st Embodiment.
That is, the control unit 20 deletes, updates, and adds the control coefficient f (x, n) in the data table by executing the data deletion process and the data addition / update process in the same procedure as in the first embodiment. The control coefficient f (x, n) in the data table is made to correspond to the position and noise level of a communication terminal that exists around the terminal and can actually communicate.

  Further, the control unit 20 controls the transmission power of the transmission signal output from the high frequency amplifier 16 and the modulation scheme / coding rate in the modulation unit 12 using the data table generated / updated as described above, and the noise Based on the noise level of the own terminal measured by the level measuring unit 40, the CS level in the demodulating unit 36 is controlled.

  Then, when controlling the transmission power, the control unit 20 selects the largest control coefficient F (x, n) from the data table stored in the storage unit 22, and the selected maximum control coefficient F (X, n) and the transmission power setting map shown in FIG. 12A are used to set the transmission power to be controlled, and to set the gain of the high-frequency amplifier 16 so that the transmission power becomes the set value. adjust.

  Further, the control unit 20 selects the largest control coefficient F (x, n) from the data table stored in the storage unit 22 when controlling the modulation scheme / coding rate, and the selected Using the maximum control coefficient F (x, n) and the transmission rate setting map shown in FIG. 12 (b), the transmission rate is set, and the modulation scheme of the modulation unit 12 so as to realize the set transmission rate. Alternatively, the coding rate is controlled.

  As a result, for example, the parameters of Equation 1 are set to “xmax: 200 m”, “nmax: −80 dBm”, “j: 0.5”, “k: 0.5”, and FIG. Are set to “threshold 1: 0.5”, “threshold 2: 1.0”, “basic transmission power: 10 dBm”, and “maximum transmission power: 20 dBm”. In the communication terminals a and e shown in FIG. 11, the transmission power is controlled as follows.

  That is, in communication terminal a, “0.625” is selected as the maximum control coefficient F (x, n), and the transmission power is “12.5 dBm” based on the selected maximum control coefficient F (x, n). In the communication terminal e, “1” is selected as the maximum control coefficient F (x, n), and the transmission power is “20 dBm” based on the selected maximum control coefficient F (x, n). Controlled.

  As described above, in the wireless communication device 2 of the present embodiment, the distance x between the surrounding communication terminals is calculated based on the position data acquired from the surrounding communication terminals and the position data of the own terminal, A data table used for controlling transmission power and transmission rate (modulation scheme / coding rate) by calculating a control coefficient f (x, n) based on the distance and noise level data acquired from surrounding communication terminals. Remember as. When each of these communication parameters is controlled, the maximum control coefficient F (x, n) in the data table is selected, and based on the maximum control coefficient F (x, n), transmission power and transmission rate ( Control modulation method and coding rate.

  For this reason, according to the wireless communication device 2 of the present embodiment, communication parameters used for data transmission according to not only the noise level on the surrounding communication terminal side that is the communication partner but also the distance to the communication terminal. Can be set.

In the present embodiment, the CS level is controlled based on the noise level around the terminal itself.
Therefore, according to the present embodiment, the communication parameter used for data transmission and the communication parameter used for data reception can be controlled to the lowest level, and noise between the own terminal and other communication terminals can be controlled. Even when there is a difference in level, it becomes possible to perform extremely good communication that is hardly affected by the interference wave.

  In the present embodiment, the modulation unit 12, the frequency converter 14, and the high frequency amplifier 16 constituting the transmission unit 10 correspond to the transmission unit of the present invention, and the control unit 20 includes the control unit and the distance calculation of the present invention. The storage unit 22 corresponds to the storage means of the present invention. Further, the high-frequency amplifier 32, the frequency converter 34, and the demodulation unit 36 constituting the receiving unit 30 correspond to the receiving unit of the present invention, and the noise level measuring unit 40 corresponds to the measuring unit of the present invention.

  In this embodiment, the maximum control coefficient F (x, n) is selected from the data table and the transmission communication parameter is controlled. However, the control coefficient used for this control includes: You may make it use the average value and median value of all the control coefficients f (x, n) in a data table. Further, the transmission power and the modulation scheme / coding rate may be controlled using different control coefficients, for example, the maximum control coefficient and the average value of the control coefficients.

It is a block diagram showing the structure of the radio | wireless communication apparatus of 1st Embodiment. It is explanatory drawing showing the structure of the transmission packet of 1st Embodiment. It is explanatory drawing showing the structure of the noise table produced | generated by 1st Embodiment. It is a flowchart showing the production | generation / update procedure of a noise table. It is explanatory drawing showing the control characteristic of transmission power and CS level based on a noise level. It is explanatory drawing showing the example of control of the transmission power and CS level in a some communication terminal. FIG. 11 is an explanatory diagram illustrating a configuration of a wireless communication apparatus according to Modification 1 and control characteristics of a transmission rate. FIG. 10 is an explanatory diagram illustrating a control example of transmission power and CS level by a wireless communication device according to a second modification. It is a block diagram showing the structure of the radio | wireless communication apparatus of 2nd Embodiment. It is explanatory drawing showing the structure of the transmission packet of 2nd Embodiment. It is explanatory drawing showing the structure of the data table produced | generated by 2nd Embodiment. It is explanatory drawing showing the control characteristic of the transmission power and transmission rate based on a maximum control coefficient.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Wireless communication apparatus, 4 ... Antenna, 6 ... Transmission / reception switching part, 10 ... Transmission part, 12 ... Modulation part, 14 ... Frequency converter, 16 ... High frequency amplifier, 20 ... Control part, 22 ... Memory | storage part, 30 ... Reception 32, a high frequency amplifier, 34, a frequency converter, 36, a demodulator, 40, a noise level measuring unit.

Claims (15)

A wireless communication device used in a wireless communication system in which a plurality of communication terminals perform wireless communication via a common wireless communication channel,
Measuring means for measuring ambient noise levels in the wireless communication channel;
Transmitting means for transmitting the noise level measured by the measuring means to the plurality of communication terminals as part of transmission data;
Receiving means for receiving transmission radio waves from the plurality of communication terminals, restoring received data, and extracting a noise level around the communication terminal that has transmitted the received data from the restored received data;
Control for controlling communication parameters for performing wireless communication with a plurality of other communication terminals based on the noise level measured by the measuring unit and the plurality of noise levels extracted by the receiving unit Means,
A wireless communication apparatus comprising: The control means includes
A storage means for storing the noise level extracted by the receiving means for each communication terminal that has transmitted the noise level;
Controlling the communication parameter based on a plurality of noise levels stored in the storage means and the noise level measured by the measuring means;
The wireless communication apparatus according to claim 1, wherein the noise level stored in the storage unit is added, updated, or deleted according to a noise level extraction state by the reception unit.   The control means selects the largest noise level from the noise level measured by the measuring means and the plurality of noise levels extracted by the receiving means, and based on the selected noise level, the communication The wireless communication apparatus according to claim 1, wherein the parameter is controlled.   The control means calculates an average value or median value of noise levels based on the noise level measured by the measuring means and a plurality of noise levels extracted by the receiving means, and the calculated average value or median The wireless communication apparatus according to claim 1, wherein the communication parameter is controlled based on a value.   The control unit controls at least one of transmission power of transmission data from the transmission unit, a modulation method of transmission data, and a coding rate of transmission data as a communication parameter. The wireless communication apparatus according to claim 4.   6. The radio communication apparatus according to claim 1, wherein the control unit controls at least one of a carrier sense level and a reception sensitivity in the receiving unit as a communication parameter. The control means includes
Based on a plurality of noise levels extracted by the reception means, control at least one of transmission power of transmission data from the transmission means, modulation method of transmission data, and coding rate of transmission data,
3. The wireless communication apparatus according to claim 1, wherein at least one of a carrier sense level and reception sensitivity in the receiving unit is controlled based on a noise level measured by the measuring unit. A wireless communication device used in a wireless communication system in which a plurality of communication terminals perform wireless communication via a common wireless communication channel,
Measuring means for measuring ambient noise levels in the wireless communication channel;
Transmission means for transmitting the noise level measured by the measurement means and position data representing the position of the wireless communication device to the plurality of communication terminals as part of transmission data;
Receiving means for receiving transmission radio waves from the plurality of communication terminals, restoring received data, and extracting noise level and position data around the communication terminal that has transmitted the received data from the restored received data;
Distance calculation means for calculating a distance between the communication terminal corresponding to the position data and the wireless communication device based on the position data extracted by the reception means;
Control communication parameters for performing wireless communication with a plurality of other communication terminals based on a plurality of noise levels extracted by the receiving unit and a plurality of distances calculated by the distance calculating unit. Control means to
A wireless communication apparatus comprising:   The control means calculates a plurality of control coefficients corresponding to the communication terminal that has transmitted the reception data based on the noise level extracted by the reception means and the distance calculated by the distance calculation means, 9. The wireless communication apparatus according to claim 8, wherein the communication parameter is controlled based on the plurality of control coefficients. The control means includes
A storage means for storing the control coefficient calculated based on the noise level and the distance for each communication terminal corresponding to the control coefficient;
The control means controls the control parameter based on a plurality of control coefficients stored in the storage means,
The wireless communication apparatus according to claim 9, wherein the control coefficient stored in the storage unit is added / updated / deleted according to a noise level and a position data extraction state in the receiving unit.   11. The control unit according to claim 9 or 10, wherein the control unit selects the largest control coefficient from the plurality of control coefficients and controls the communication parameter based on the selected control coefficient. Wireless communication device.   The control means calculates an average value or median value of the plurality of control coefficients, and controls the communication parameter based on the calculated average value or median value. The wireless communication device described.   The control means controls at least one of transmission power of transmission data from the transmission means, a modulation scheme of transmission data, and a coding rate of transmission data based on the control coefficient. The wireless communication apparatus according to any one of claims 9 to 12.   The wireless communication apparatus according to claim 9, wherein the control unit controls at least one of a carrier sense level and a reception sensitivity in the reception unit based on the control coefficient. The control means includes
Based on the control coefficient, control at least one of transmission power of transmission data from the transmission means, modulation scheme of transmission data, and coding rate of transmission data,
The radio communication apparatus according to claim 9 or 10, wherein at least one of a carrier sense level and reception sensitivity in the receiving unit is controlled based on a noise level measured by the measuring unit.

Images